"The Treasury Department’s Financial Crimes Enforcement Network, FinCEN, shows on their website that Mt. Gox’s registration as a money services business was received on Thursday 27th June.
Although the registration does not constitute approval by FinCEN of Mt. Gox’s activities, it is a sign that the bitcoin exchange is willing to abide by US rules in order to continue operating.
FinCEN issued guidelines applying traditional money-laundering rules to virtual currenciesin March amid concerns over the involvement of virtual currencies in money laundering. FinCEN stated that virtual currency exchanges must register with them as money transmitters and must comply with anti-money-laundering regulations. Although bitcoin was not mentioned by name in the guidelines, it was clearly implicated by mention of “decentralised virtual currencies”."
Source Article - Coindesk